Btw, TestException#test_machine_stackoverflow_by_define_method fails
on an ancient glibc 2.5-42.el5_4.3 (CentOS 5.4 x86_64).

I think this is a bug in pthread_getattr_np when it is run on the main
thread.  I'm not sure how many people care about a platform this old,
though; and I've been meaning to upgrade that anyways.